HeparinaseⅠis an enzyme that specifically cleaves certain sequences of heparan sulfate. Previous reports showed that this enzyme was highly prone to aggregation in inclusion bodies when it was expressed in Escherichia coli. In this paper, the N-terminus of heparinaseⅠgene was fused a glutathione-S-transferase (GST) tag, which expressed the fusion protein in Escherichia coli. The results showed when induced at 15 ℃, approximately 90% of the fusion protein was found to be produced in the soluble. The enzyme has a specific activity of 124.7 U/mg protein by one-step affinity chromatography, the recovery was 31.0%, and a 366.7-fold-purification was achieved. GST-Hep I was well activated by Ca2+
. Results of GPC-HPLC (Gel permeation chromatography high-performance liquid chromatography) analysis of oligosaccharides of heparin degraded by GST-HepⅠ was similar to those of native Hep Ⅰ.